This invention relates to an improved system for igniting shock tube or detonation cord to achieve safe ignition of explosive material.
The safe ignition of explosives continues to be a problem. In a typical system detonation cord or shock tube is used to ignite the explosive materials. Both detonation cord and shock tube contain explosive materials and when the proximal end detonation cord or shock tube is ignited an explosion will travel along the length of the detonation cord or shock tube to the remote end of the shock tube to ignite explosive material at the remote end of the detonation cord or shock tube, usually by means of a blasting cap. Hereinafter detonation cord and shock tube are generically referred to as explosion transmitting line, which is defined to mean a line which will transmit a traveling explosion when ignited. A typical way of igniting the proximal end of explosion transmitting line is by means of a blasting cap. Since blasting caps are themselves dangerous and frequently cause injures to the personnel using them, there is a need to improve the safety of the system used to ignite explosion transmitting line. In application Ser. No. 09/296287, filed Apr. 22, 1999 by Richard Snyder, the inventor of this application, there is disclosed a system in which the proximal end of shock tube is ignited by means of a hot high voltage spark which showers the proximal end of the shock tube with molten copper particles to provide reliable ignition of the shock tube. To further improve the safety of the system, the ignition spark is triggered by radio transmission. While the above described system is effective in providing safe reliable ignition of shock tube, it is not very effective in providing reliable ignition of detonation cord, which is harder to ignite. The system of the prior application is relatively expensive to use because the probe which defines the spark gap is relatively expensive and the probes are destroyed when they are used. Accordingly there is a need for a less expensive highly reliable and safe explosion transmitting line ignition system.
In accordance with the present invention the proximal end of the explosion transmitting line is ignited by means of a plated through-hole of a printed circuit board. The end of the explosion transmitting line is threaded through the plated. through-hole and is knotted to secure the explosion transmitting line in position in the through-hole. To ignite the explosion transmitting line, a high voltage from a high current source is applied across the through-hole. This high voltage and high current will cause the plated through-hole to explode and ignite the explosion transmitting line. In this manner safe and reliable ignition is achieved at very little cost because the plated through-hole is the same as those found in conventional printed circuit boards and is very inexpensive to manufacture.